diff options
Diffstat (limited to 'v4l2-spec/dev-sliced-vbi.sgml')
| -rw-r--r-- | v4l2-spec/dev-sliced-vbi.sgml | 359 |
1 files changed, 336 insertions, 23 deletions
diff --git a/v4l2-spec/dev-sliced-vbi.sgml b/v4l2-spec/dev-sliced-vbi.sgml index 5560650a6..a2cfc45ef 100644 --- a/v4l2-spec/dev-sliced-vbi.sgml +++ b/v4l2-spec/dev-sliced-vbi.sgml @@ -48,7 +48,7 @@ vital to program a sliced VBI device, therefore must be supported.</para> </section> - <section> + <section id="sliced-vbi-format-negotitation"> <title>Sliced VBI Format Negotiation</title> <para>To find out which data services are supported by the @@ -96,12 +96,12 @@ points which may return <errorcode>EBUSY</errorcode> can be the <title>struct <structname>v4l2_sliced_vbi_format</structname></title> <tgroup cols="5"> - <colspec colname="c1" colwidth="3*"> - <colspec colname="c2" colwidth="3*"> - <colspec colname="c3" colwidth="2*"> - <colspec colname="c4" colwidth="2*"> - <colspec colname="c5" colwidth="2*"> - <spanspec namest="c3" nameend="c5" spanname="hspan"> + <colspec colname="c1" colwidth="3*" /> + <colspec colname="c2" colwidth="3*" /> + <colspec colname="c3" colwidth="2*" /> + <colspec colname="c4" colwidth="2*" /> + <colspec colname="c5" colwidth="2*" /> + <spanspec namest="c3" nameend="c5" spanname="hspan" /> <tbody valign="top"> <row> <entry>__u32</entry> @@ -139,9 +139,9 @@ return the requested set, a subset, which may be just a single service, or an empty set. When the hardware cannot handle multiple services on the same line the driver shall choose one. No assumptions can be made on which service the driver chooses.</para><para>Data -services are defined in <xref linkend="vbi-services2">. Array indices -map to ITU-R line numbers (see also <xref linkend="vbi-525"> and <xref - linkend="vbi-625">) as follows: <!-- No nested +services are defined in <xref linkend="vbi-services2" />. Array indices +map to ITU-R line numbers (see also <xref linkend="vbi-525" /> and <xref + linkend="vbi-625" />) as follows: <!-- No nested tables, sigh. --></para></entry> </row> <row> @@ -211,12 +211,12 @@ extensions. Applications and drivers must set it to zero.</entry> <table frame="none" pgwide="1" id="vbi-services2"> <title>Sliced VBI services</title> <tgroup cols="5"> - <colspec colname="c1" colwidth="2*"> - <colspec colname="c2" colwidth="1*"> - <colspec colname="c3" colwidth="1*"> - <colspec colname="c4" colwidth="2*"> - <colspec colname="c5" colwidth="2*"> - <spanspec namest="c3" nameend="c5" spanname="rlp"> + <colspec colname="c1" colwidth="2*" /> + <colspec colname="c2" colwidth="1*" /> + <colspec colname="c3" colwidth="1*" /> + <colspec colname="c4" colwidth="2*" /> + <colspec colname="c5" colwidth="2*" /> + <spanspec namest="c3" nameend="c5" spanname="rlp" /> <thead> <row> <entry>Symbol</entry> @@ -231,7 +231,7 @@ extensions. Applications and drivers must set it to zero.</entry> <entry><constant>V4L2_SLICED_TELETEXT_B</constant> (Teletext System B)</entry> <entry>0x0001</entry> - <entry><xref linkend="ets300706">, <xref linkend="itu653"></entry> + <entry><xref linkend="ets300706" />, <xref linkend="itu653" /></entry> <entry>PAL/SECAM line 7-22, 320-335 (second field 7-22)</entry> <entry>Last 42 of the 45 byte Teletext packet, that is without clock run-in and framing code, lsb first transmitted.</entry> @@ -239,7 +239,7 @@ without clock run-in and framing code, lsb first transmitted.</entry> <row> <entry><constant>V4L2_SLICED_VPS</constant></entry> <entry>0x0400</entry> - <entry><xref linkend="ets300231"></entry> + <entry><xref linkend="ets300231" /></entry> <entry>PAL line 16</entry> <entry>Byte number 3 to 15 according to Figure 9 of ETS 300 231, lsb first transmitted.</entry> @@ -247,7 +247,7 @@ ETS 300 231, lsb first transmitted.</entry> <row> <entry><constant>V4L2_SLICED_CAPTION_525</constant></entry> <entry>0x1000</entry> - <entry><xref linkend="eia608"></entry> + <entry><xref linkend="eia608" /></entry> <entry>NTSC line 21, 284 (second field 21)</entry> <entry>Two bytes in transmission order, including parity bit, lsb first transmitted.</entry> @@ -255,7 +255,7 @@ bit, lsb first transmitted.</entry> <row> <entry><constant>V4L2_SLICED_WSS_625</constant></entry> <entry>0x4000</entry> - <entry><xref linkend="itu1119">, <xref linkend="en300294"></entry> + <entry><xref linkend="itu1119" />, <xref linkend="en300294" /></entry> <entry>PAL/SECAM line 23</entry> <entry><screen> Byte 0 1 @@ -311,7 +311,7 @@ zero.</para> <row> <entry>__u32</entry> <entry><structfield>id</structfield></entry> - <entry>A flag from <xref linkend="vbi-services"> + <entry>A flag from <xref linkend="vbi-services" /> identifying the type of data in this packet. Only a single bit must be set. When the <structfield>id</structfield> of a captured packet is zero, the packet is empty and the contents of other fields are @@ -334,7 +334,7 @@ field, <constant>1</constant> for the second field.</entry> <entry><structfield>line</structfield></entry> <entry>The field (as opposed to frame) line number this data has been captured from, or shall be inserted at. See <xref - linkend="vbi-525"> and <xref linkend="vbi-625"> for valid + linkend="vbi-525" /> and <xref linkend="vbi-625" /> for valid values. Sliced VBI capture devices can set the line number of all packets to <constant>0</constant> if the hardware cannot reliably identify scan lines. The field number must always be valid.</entry> @@ -349,7 +349,7 @@ Applications and drivers must set it to zero.</entry> <entry>__u8</entry> <entry><structfield>data</structfield>[48]</entry> <entry>The packet payload. See <xref - linkend="vbi-services"> for the contents and number of + linkend="vbi-services" /> for the contents and number of bytes passed for each data type. The contents of padding bytes at the end of this array are undefined, drivers and applications shall ignore them.</entry> @@ -386,6 +386,319 @@ video and VBI data by using buffer timestamps.</para> </section> + <section> + <title>Sliced VBI Data in MPEG Streams</title> + + <para>If a device can produce an MPEG output stream, it may be +capable of providing <link +linkend="sliced-vbi-format-negotitation">negotiated sliced VBI +services</link> as data embedded in the MPEG stream. Users or +applications control this sliced VBI data insertion with the <link +linkend="v4l2-mpeg-stream-vbi-fmt">V4L2_CID_MPEG_STREAM_VBI_FMT</link> +control.</para> + + <para>If the driver does not provide the <link +linkend="v4l2-mpeg-stream-vbi-fmt">V4L2_CID_MPEG_STREAM_VBI_FMT</link> +control, or only allows that control to be set to <link +linkend="v4l2-mpeg-stream-vbi-fmt"><constant> +V4L2_MPEG_STREAM_VBI_FMT_NONE</constant></link>, then the device +cannot embed sliced VBI data in the MPEG stream.</para> + + <para>The <link linkend="v4l2-mpeg-stream-vbi-fmt"> +V4L2_CID_MPEG_STREAM_VBI_FMT</link> control does not implicitly set +the device driver to capture nor cease capturing sliced VBI data. The +control only indicates to embed sliced VBI data in the MPEG stream, if +an application has negotiated sliced VBI service be captured.</para> + + <para>It may also be the case that a device can embed sliced VBI +data in only certain types of MPEG streams: for example in an MPEG-2 +PS but not an MPEG-2 TS. In this situation, if sliced VBI data +insertion is requested, the sliced VBI data will be embedded in MPEG +stream types when supported, and silently omitted from MPEG stream +types where sliced VBI data insertion is not supported by the device. +</para> + + <para>The following subsections specify the format of the +embedded sliced VBI data.</para> + + <section> + <title>MPEG Stream Embedded, Sliced VBI Data Format: NONE</title> + <para>The <link linkend="v4l2-mpeg-stream-vbi-fmt"><constant> +V4L2_MPEG_STREAM_VBI_FMT_NONE</constant></link> embedded sliced VBI +format shall be interpreted by drivers as a control to cease +embedding sliced VBI data in MPEG streams. Neither the device nor +driver shall insert "empty" embedded sliced VBI data packets in the +MPEG stream when this format is set. No MPEG stream data structures +are specified for this format.</para> + </section> + + <section> + <title>MPEG Stream Embedded, Sliced VBI Data Format: IVTV</title> + <para>The <link linkend="v4l2-mpeg-stream-vbi-fmt"><constant> +V4L2_MPEG_STREAM_VBI_FMT_IVTV</constant></link> embedded sliced VBI +format, when supported, indicates to the driver to embed up to 36 +lines of sliced VBI data per frame in an MPEG-2 <emphasis>Private +Stream 1 PES</emphasis> packet encapsulated in an MPEG-2 <emphasis> +Program Pack</emphasis> in the MPEG stream.</para> + + <para><emphasis>Historical context</emphasis>: This format +specification originates from a custom, embedded, sliced VBI data +format used by the <filename>ivtv</filename> driver. This format +has already been informally specified in the kernel sources in the +file <filename>Documentation/video4linux/cx2341x/README.vbi</filename> +. The maximum size of the payload and other aspects of this format +are driven by the CX23415 MPEG decoder's capabilities and limitations +with respect to extracting, decoding, and displaying sliced VBI data +embedded within an MPEG stream.</para> + + <para>This format's use is <emphasis>not</emphasis> exclusive to +the <filename>ivtv</filename> driver <emphasis>nor</emphasis> +exclusive to CX2341x devices, as the sliced VBI data packet insertion +into the MPEG stream is implemented in driver software. At least the +<filename>cx18</filename> driver provides sliced VBI data insertion +into an MPEG-2 PS in this format as well.</para> + + <para>The following definitions specify the payload of the +MPEG-2 <emphasis>Private Stream 1 PES</emphasis> packets that contain +sliced VBI data when <link linkend="v4l2-mpeg-stream-vbi-fmt"> +<constant>V4L2_MPEG_STREAM_VBI_FMT_IVTV</constant></link> is set. +(The MPEG-2 <emphasis>Private Stream 1 PES</emphasis> packet header +and encapsulating MPEG-2 <emphasis>Program Pack</emphasis> header are +not detailed here. Please refer to the MPEG-2 specifications for +details on those packet headers.)</para> + + <para>The payload of the MPEG-2 <emphasis>Private Stream 1 PES +</emphasis> packets that contain sliced VBI data is specified by +&v4l2-mpeg-vbi-fmt-ivtv;. The payload is variable +length, depending on the actual number of lines of sliced VBI data +present in a video frame. The payload may be padded at the end with +unspecified fill bytes to align the end of the payload to a 4-byte +boundary. The payload shall never exceed 1552 bytes (2 fields with +18 lines/field with 43 bytes of data/line and a 4 byte magic number). +</para> + + <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-fmt-ivtv"> + <title>struct <structname>v4l2_mpeg_vbi_fmt_ivtv</structname> + </title> + <tgroup cols="4"> + &cs-ustr; + <tbody valign="top"> + <row> + <entry>__u8</entry> + <entry><structfield>magic</structfield>[4]</entry> + <entry></entry> + <entry>A "magic" constant from <xref + linkend="v4l2-mpeg-vbi-fmt-ivtv-magic" /> that indicates +this is a valid sliced VBI data payload and also indicates which +member of the anonymous union, <structfield>itv0</structfield> or +<structfield>ITV0</structfield>, to use for the payload data.</entry> + </row> + <row> + <entry>union</entry> + <entry>(anonymous)</entry> + </row> + <row> + <entry></entry> + <entry>struct <link linkend="v4l2-mpeg-vbi-itv0"> + <structname>v4l2_mpeg_vbi_itv0</structname></link> + </entry> + <entry><structfield>itv0</structfield></entry> + <entry>The primary form of the sliced VBI data payload +that contains anywhere from 1 to 35 lines of sliced VBI data. +Line masks are provided in this form of the payload indicating +which VBI lines are provided.</entry> + </row> + <row> + <entry></entry> + <entry>struct <link linkend="v4l2-mpeg-vbi-ITV0-1"> + <structname>v4l2_mpeg_vbi_ITV0</structname></link> + </entry> + <entry><structfield>ITV0</structfield></entry> + <entry>An alternate form of the sliced VBI data payload +used when 36 lines of sliced VBI data are present. No line masks are +provided in this form of the payload; all valid line mask bits are +implcitly set.</entry> + </row> + </tbody> + </tgroup> + </table> + + <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-fmt-ivtv-magic"> + <title>Magic Constants for &v4l2-mpeg-vbi-fmt-ivtv; + <structfield>magic</structfield> field</title> + <tgroup cols="3"> + &cs-def; + <thead> + <row> + <entry align="left">Defined Symbol</entry> + <entry align="left">Value</entry> + <entry align="left">Description</entry> + </row> + </thead> + <tbody valign="top"> + <row> + <entry><constant>V4L2_MPEG_VBI_IVTV_MAGIC0</constant> + </entry> + <entry>"itv0"</entry> + <entry>Indicates the <structfield>itv0</structfield> +member of the union in &v4l2-mpeg-vbi-fmt-ivtv; is valid.</entry> + </row> + <row> + <entry><constant>V4L2_MPEG_VBI_IVTV_MAGIC1</constant> + </entry> + <entry>"ITV0"</entry> + <entry>Indicates the <structfield>ITV0</structfield> +member of the union in &v4l2-mpeg-vbi-fmt-ivtv; is valid and +that 36 lines of sliced VBI data are present.</entry> + </row> + </tbody> + </tgroup> + </table> + + <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-itv0"> + <title>struct <structname>v4l2_mpeg_vbi_itv0</structname> + </title> + <tgroup cols="3"> + &cs-str; + <tbody valign="top"> + <row> + <entry>__le32</entry> + <entry><structfield>linemask</structfield>[2]</entry> + <entry><para>Bitmasks indicating the VBI service lines +present. These <structfield>linemask</structfield> values are stored +in little endian byte order in the MPEG stream. Some reference +<structfield>linemask</structfield> bit positions with their +corresponding VBI line number and video field are given below. +b<subscript>0</subscript> indicates the least significant bit of a +<structfield>linemask</structfield> value:<screen> +<structfield>linemask</structfield>[0] b<subscript>0</subscript>: line 6 first field +<structfield>linemask</structfield>[0] b<subscript>17</subscript>: line 23 first field +<structfield>linemask</structfield>[0] b<subscript>18</subscript>: line 6 second field +<structfield>linemask</structfield>[0] b<subscript>31</subscript>: line 19 second field +<structfield>linemask</structfield>[1] b<subscript>0</subscript>: line 20 second field +<structfield>linemask</structfield>[1] b<subscript>3</subscript>: line 23 second field +<structfield>linemask</structfield>[1] b<subscript>4</subscript>-b<subscript>31</subscript>: unused and set to 0</screen></para></entry> + </row> + <row> + <entry>struct <link linkend="v4l2-mpeg-vbi-itv0-line"> + <structname>v4l2_mpeg_vbi_itv0_line</structname></link> + </entry> + <entry><structfield>line</structfield>[35]</entry> + <entry>This is a variable length array that holds from 1 +to 35 lines of sliced VBI data. The sliced VBI data lines present +correspond to the bits set in the <structfield>linemask</structfield> +array, starting from b<subscript>0</subscript> of <structfield> +linemask</structfield>[0] up through b<subscript>31</subscript> of +<structfield>linemask</structfield>[0], and from b<subscript>0 +</subscript> of <structfield>linemask</structfield>[1] up through b +<subscript>3</subscript> of <structfield>linemask</structfield>[1]. +<structfield>line</structfield>[0] corresponds to the first bit +found set in the <structfield>linemask</structfield> array, +<structfield>line</structfield>[1] corresponds to the second bit +found set in the <structfield>linemask</structfield> array, etc. +If no <structfield>linemask</structfield> array bits are set, then +<structfield>line</structfield>[0] may contain one line of +unspecified data that should be ignored by applications.</entry> + </row> + </tbody> + </tgroup> + </table> + + <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-ITV0-1"> + <title>struct <structname>v4l2_mpeg_vbi_ITV0</structname> + </title> + <tgroup cols="3"> + &cs-str; + <tbody valign="top"> + <row> + <entry>struct <link linkend="v4l2-mpeg-vbi-itv0-line"> + <structname>v4l2_mpeg_vbi_itv0_line</structname></link> + </entry> + <entry><structfield>line</structfield>[36]</entry> + <entry>A fixed length array of 36 lines of sliced VBI +data. <structfield>line</structfield>[0] through <structfield>line +</structfield>[17] correspond to lines 6 through 23 of the +first field. <structfield>line</structfield>[18] through +<structfield>line</structfield>[35] corresponds to lines 6 +through 23 of the second field.</entry> + </row> + </tbody> + </tgroup> + </table> + + <table frame="none" pgwide="1" id="v4l2-mpeg-vbi-itv0-line"> + <title>struct <structname>v4l2_mpeg_vbi_itv0_line</structname> + </title> + <tgroup cols="3"> + &cs-str; + <tbody valign="top"> + <row> + <entry>__u8</entry> + <entry><structfield>id</structfield></entry> + <entry>A line identifier value from +<xref linkend="ITV0-Line-Identifier-Constants" /> that indicates +the type of sliced VBI data stored on this line.</entry> + </row> + <row> + <entry>__u8</entry> + <entry><structfield>data</structfield>[42]</entry> + <entry>The sliced VBI data for the line.</entry> + </row> + </tbody> + </tgroup> + </table> + + <table frame="none" pgwide="1" id="ITV0-Line-Identifier-Constants"> + <title>Line Identifiers for struct <link + linkend="v4l2-mpeg-vbi-itv0-line"><structname> +v4l2_mpeg_vbi_itv0_line</structname></link> <structfield>id +</structfield> field</title> + <tgroup cols="3"> + &cs-def; + <thead> + <row> + <entry align="left">Defined Symbol</entry> + <entry align="left">Value</entry> + <entry align="left">Description</entry> + </row> + </thead> + <tbody valign="top"> + <row> + <entry><constant>V4L2_MPEG_VBI_IVTV_TELETEXT_B</constant> + </entry> + <entry>1</entry> + <entry>Refer to <link linkend="vbi-services2"> +Sliced VBI services</link> for a description of the line payload.</entry> + </row> + <row> + <entry><constant>V4L2_MPEG_VBI_IVTV_CAPTION_525</constant> + </entry> + <entry>4</entry> + <entry>Refer to <link linkend="vbi-services2"> +Sliced VBI services</link> for a description of the line payload.</entry> + </row> + <row> + <entry><constant>V4L2_MPEG_VBI_IVTV_WSS_625</constant> + </entry> + <entry>5</entry> + <entry>Refer to <link linkend="vbi-services2"> +Sliced VBI services</link> for a description of the line payload.</entry> + </row> + <row> + <entry><constant>V4L2_MPEG_VBI_IVTV_VPS</constant> + </entry> + <entry>7</entry> + <entry>Refer to <link linkend="vbi-services2"> +Sliced VBI services</link> for a description of the line payload.</entry> + </row> + </tbody> + </tgroup> + </table> + + </section> + </section> + + <!-- Local Variables: mode: sgml |